Stereoregular diene polymers are produced and used industrially on a large scale as an important component of tire compounds. Diene polymers with high levels of stereoregularity are almost exclusively prepared with coordination polymerization catalysts, which are in general easily poisoned by polar functionalities. Because of this poisoning effect, the types of monomers that are compatible with coordination catalysts are usually limited to simple hydrocarbons. It is well known within the tire industry that the incorporation of even low levels of functionality into certain tire polymers (prepared through anionic or emulsion polymerization) significantly improves the performance of tires containing such polymers. Unfortunately, there is currently no reliable method to apply this functionalization technology to stereoregular diene polymers, but it is likely that such a polymer would show superior tire properties over known unfunctionalized polymers.
The synthesis of copolymers based on polar and nonpolar olefins via insertion polymerization is a challenging goal of polymer chemistry. Fundamental progress has been made recently in the polymerization of ethylene with polar vinyl monomers (see e.g., Chen, Chem. Rev. 2009, 109, 5157-5214; Drent et al., Chem. Commun. 2002, 744-745; Johnson et al., J. Am. Chem. Soc. 1996, 118, 267-268; Nakamura et al., Chem. Rev. 2009, 109, 5215-5244.) The functionalization of poly(dienes) via direct copolymerization with polar monomers, however, is almost exclusively accomplished by free-radical or anionic methods (see e.g., Sheares et al., J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 4070-4080; Sunada et al., J. Appl. Polym. Sci. 2005, 97, 1545-1552; Yang et al., Macromolecules 2006, 39, 8625-8631; Yang et al., Polymer 2007, 48, 105-109.) The lack of microstructure control in these polymerizations is a major drawback because the properties of the poly(dienes), and hence the applicability, are strongly dependent on the polymer microstructure. Post polymerization functionalization is widely applied in polydiene chemistry. Vulcanization in the rubber industry is a prominent example. The reactivity of sulfur compounds with double bonds was also applied in the functionalization of 1,2-polybutadiene and poly(isoprene-co-3methylenehepta-1,6-diene) via the thiol-ene reaction (see e.g., David et al., Macromolecules 2008, 41, 1151-1161; Justynska et al., Polymer 2005, 46, 12057-12064; Li et al., Macromolecules 2016; Brummelhuis, et al, Macromolecules 2008, 41, 9946-9947.) Although the functionalizations were successful, they still require additional activation, namely UV-irradiation and/or the addition of radical initiators. However, this approach cannot be utilized for high 1,4-cis poly(butadiene) (PBD) as cross-linking occurs under the functionalization conditions. A mild method for a versatile post-polymerization functionalization of 1,4-cis-poly(butadiene) with a reactivity approach orthogonal to the backbone's double bonds is highly desirable.